Viscous clutch and associated reservoir configuration

ABSTRACT

A viscous clutch ( 30; 130; 230 ) includes a shaft ( 32; 132; 232 ), a rotor ( 34; 134; 234 ) attached to the shaft, a housing ( 36; 136; 236 ) located adjacent to the rotor, a working chamber ( 40; 140; 240 ) defined between the rotor and the housing, and a reservoir ( 38; 138; 238 ) used to store a shear fluid. Selective introduction of the shear fluid to the working chamber facilitates selective torque transmission between the rotor and the housing. The reservoir is attached to the shaft separately from the rotor.

BACKGROUND

The present invention relates generally to clutches, and moreparticularly to viscous clutches.

Viscous clutches are used in a wide variety of automotive fan driveapplications, among other uses. These clutches typically employrelatively thick silicone oil (more generally called shear fluid orviscous fluid) for the selective transmission of torque between tworotatable components. It is possible to engage or disengage the clutchby selectively allowing the oil into and out of a working area of theclutch located between input and output members (e.g., between an inputrotor and an output housing). A valve is used to control the flow of theoil in the working area between the input and the output. Recent clutchdesigns have been employed that allow the oil to be stored in areservoir attached to an input rotor while the clutch is disengaged, inorder to keep kinetic energy available in the oil to allow rapidengagement of the clutch from the off condition. This also allows theclutch to have a very low output speed (e.g., fan speed) while the valveis positioned to obstruct oil flow into the working area. However,attachment of the reservoir to the rotor disk substantially limitsdesign flexibility. For instance, many prior art clutches havelimitations associated with magnetic flux circuits used for control ofthe valve, and positioning a valve relative to a rotating reservoirwhile still providing suitable fluid and flux paths presents formidablechallenges. These constraints typically apply while still seeking toprovide a relatively compact and low-mass clutch package that can stillaccommodate desired torque loads and function quickly, efficiently andreliably.

Therefore, it is desired to provide an alternative viscous clutch.

SUMMARY

In one aspect of the present disclosure, for example, a viscous clutchincludes a shaft, a rotor attached to the shaft, a housing locatedadjacent to the rotor, a working chamber defined between the rotor andthe housing, and a reservoir used to store a shear fluid. Selectiveintroduction of the shear fluid to the working chamber facilitatesselective torque transmission between the rotor and the housing. Thereservoir is attached to the shaft separately from the rotor.

The present summary is provided only by way of example, and notlimitation. Other aspects of the present disclosure will be appreciatedin view of the entirety of the present disclosure, including the entiretext, claims and accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of one embodiment of a viscous clutchaccording to the present invention.

FIG. 2 is a cross-sectional perspective view of a portion of the viscousclutch of FIG. 1, shown with a cover and rotor disk omitted forillustrative purposes only.

FIG. 3 is a cross-sectional view of a portion of a reservoir of theviscous clutch of FIGS. 1 and 2, shown in isolation.

FIG. 4 is a perspective view of a rotor disk and the reservoir of FIGS.1-3, shown in isolation.

FIGS. 1A-1C are cross-sectional views of alternate embodiments of theviscous clutch of FIG. 1.

FIG. 5 is a cross-sectional view of another embodiment of a viscousclutch according to the present invention.

FIG. 6 is a cross-sectional view of another embodiment of a viscousclutch according to the present invention.

FIG. 7 is a partial cross-sectional view of another embodiment of aviscous clutch according to the present invention.

FIG. 8 is a partial cross-sectional view of another embodiment of aviscous clutch according to the present invention.

FIG. 9 is a partial cross-sectional view of yet another embodiment of aviscous clutch according to the present invention.

While the above-identified figures set forth embodiments of the presentdisclosure, other embodiments are also contemplated, as noted in thediscussion. In all cases, this disclosure presents the invention by wayof representation and not limitation. It should be understood thatnumerous other modifications and embodiments can be devised by thoseskilled in the art, which fall within the scope and spirit of theprinciples of the invention. The figures may not be drawn to scale, andapplications and embodiments of the present invention may includefeatures and components not specifically shown in the drawings.

DETAILED DESCRIPTION

In general, the present invention provides a viscous clutch (also calleda fluid friction coupling, liquid friction clutch, or the like) thatdecouples or separates a reservoir and a valve from a rotor disk thatprovides a rotational input to the clutch. The reservoir can be coupledto an input shaft and thus can rotate with the input shaft to providekinetic energy to the reservoir and any fluid that the reservoircontains. A separate reservoir provides various advantages and benefits,such as improved abilities to control and adjust fluid flow from thereservoir to a working chamber, as well as allowing portions of amagnetic flux circuit (e.g., for controlling a valve) to be integratedinto the reservoir to help provide a relatively compact and lightweightoverall clutch package without a need for the flux circuit to traversethe rotor disk. Certain other features of the present invention aredescribed further below, such as a generally annular contour or toroidalridge in a wall of the reservoir to accommodate a protruding fluxinsert, a fluid bore having an angled (clocked) offset relative to ahole in the rotor disk, a fluid return bore that passes through a fluxguide insert, and a slot-shaped return bore outlet. Persons of ordinaryskill in the art will recognize numerous additional features andbenefits of the invention in view of the attached figures and thedescription that follows. Moreover, it should be noted that whilevarious preferred embodiments are shown and described herein, thoseembodiments are shown and described merely by way of example and notlimitation, and additional embodiments are contemplated within the scopeof the present invention.

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 61/782,440, entitled “Viscous Clutch With SeparateReservoir or Rotatable Reservoir,” filed Mar. 14, 2013, which is herebyincorporated by reference in its entirety.

FIGS. 1 and 2 illustrate one embodiment of a viscous clutch 30 that canbe used to selectively drive a fan or other output component (not shown)as a function of a torque input to the clutch 30. FIG. 1 is across-sectional view of the clutch 30, and FIG. 2 is a cross-sectionalperspective view of a portion of the clutch 30 with portions omitted tobetter reveal interior structures. The illustrated embodiment of theclutch 30 includes a drive (input) shaft 32, a rotor disk (or rotor) 34,a housing 36, a reservoir 38, a working chamber 40, a valve assembly 42,and an electromagnetic coil 44 (also called a solenoid). Additionalcomponents of the clutch 30 are discussed further below.

The drive shaft 32 has a first end 32-1 and an opposite second end 32-2,and can accept a rotational input to the clutch 30, such as from anothershaft, a pulley, etc. (not shown). The drive shaft 32 is considered a“live” shaft because it rotates whenever there is a rotational input tothe clutch 30. The drive shaft 32 provides structural support for othercomponents of the clutch 30, and facilitates transmission of torque tocertain other components. For instance, the first end 32-1 can beconnected to a torque input and delivered at or near the second end32-2. The drive shaft 32 generally defines an axis A of the clutch 32.It should be noted that the particular configuration of the shaft 32 isshown and described merely by way of example, and not limitation, andcan vary as desired for particular applications. For instance, thepresent invention could be implemented with a clutch having a stationaryshaft, in alternative embodiments.

The rotor disk 34 can be fixedly attached to the drive shaft 32 torotate with the drive shaft 32. It should be noted that the rotor disk34 is omitted in FIG. 2 merely for illustrative purposes, in order tobetter reveal other components of the clutch 30. In the illustratedembodiment, as shown in FIG. 1, the rotor disk 34 is connected at ornear the second end 32-2 of the drive shaft 32 and can act as arotational (torque) input member for the clutch 30. Moreover, in theillustrated embodiment, the rotor disk 34 includes an inner diameterinsert 34-1 and an outer diameter portion 34-2. Ribs 34-3 or othersuitable structures can be provided on one or both sides of the rotordisk 34 at or along the working chamber 40 (e.g., at the outer diameterportion 34-2). Additionally, a notch 34-4 can optionally be provided inthe rotor disk 34 (e.g., at the outer diameter portion 34-2) to provideadditional clearance for the valve assembly 42 (e.g., clearance in agenerally axial direction). Still further, one or more holes (orwindows) 34-5 can be provided through the rotor disk 34 (e.g., at theouter diameter portion 34-2) to allow shear fluid (e.g., silicone oil)to pass between opposite sides of the rotor disk 34 (see also FIG. 4).The particular configuration of the rotor disk 34 is shown and describedmerely by way of example, and not limitation, and can vary as desiredfor particular applications.

The housing 36 generally surrounds the rotor disk 34 and can act as arotational (torque) output member, when the clutch 30 is selectivelyengaged. A further output element, such as a fan, pulley, output shaft,gear, pump, etc. (not shown), can be connected to the housing 36 toreceive torque output from the clutch 30, as desired for particularapplications. The housing 36 can be made in two parts, with a body 36-1and a cover 36-2. The cover 36-2 is omitted in FIG. 2 merely forillustrative purposes, to better reveal interior components of theclutch 30. In the illustrated embodiment, the housing 36 is rotatablysupported on the drive shaft 32 by suitable bearings 46. Cooling fins36-3 can optionally be provided on an exterior of the housing 36 in aconventional manner to facilitate dissipation of thermal energy intoambient air. Again, it should be noted that the particular configurationof the housing 36 is shown and described merely by way of example, andnot limitation, and can vary as desired for particular applications.

A flux insert (or flux guide) 48 can extend through the body 36-1 tohelp guide magnetic flux generated by the electromagnetic coil 44through the housing 36 to control operation of the valve assembly 42. Inthe illustrated embodiment, the flux insert 48 includes a first end 48-1positioned proximate to the electromagnetic coil 44 (i.e., within a fluxrange of the coil 44), an opposite second end 48-2, and one or moreopenings 48-3. The second end 48-2 can be radially offset relative tothe first end 48-1. One or both of the first and second ends 48-1 and48-2 of the flux insert 48 can stand proud from the housing 36. Forinstance, in the illustrated embodiment the second end 48-2 axiallyprotrudes into an interior cavity of the housing 36 adjacent to thereservoir 38, and the first end 48-1 axially protrudes from the housing36 adjacent to the electromagnetic coil 44. The one or more openings48-3 can be located in a generally middle region of the flux insert 48,in between the first and second ends 48-1 and 48-2. The openings 48-3can help reduce a mass of the flux insert 48, help allow the flux insert48 to be firmly retained by the housing 36, and provide other benefitsdiscussed further below. The flux insert 48 can be made of a magneticflux conducting material, such as non-alloyed iron, steel, etc., andmaterial of the body 36-1 of the housing 36 (e.g., aluminum) can be castabout the flux insert 48 to secure the insert 48 therein. The embodimentof the flux insert 48 is shown and described merely by way of example,and can be implemented in alternative embodiments as desired forparticular applications.

The reservoir 38 can be positioned within the housing 36, and can befixedly attached to the drive shaft 32 to rotate with the drive shaft 32whenever a torque input to the shaft 32 is present. The reservoir 38 canhold a supply of shear fluid during at least some operating conditionsof the clutch 30, with the reservoir 38 typically holding a majority ofthe shear fluid when the clutch 30 is in a disengaged condition.Rotation of the reservoir 38 when a torque input is provided to theclutch 30 can impart kinetic energy to shear fluid contained in thereservoir 38, which can help provide relatively quick engagement of theclutch 30.

The reservoir 38 can be configured as a multi-piece assembly thatincludes a first (or inner) piece 38-1, a second (or intermediate) piece38-2, a third (or outer) piece 38-3, and a fourth (or cap) piece 38-4,though in further embodiments the reservoir 38 could be constructed froma larger or smaller number of discrete pieces. The first piece 38-1 canbe positioned generally radially inwardly and attached directly to thedrive shaft 32, and can have a generally planar, disk-like shape. Thesecond piece 38-2 can also have a generally planar, disk-like shape, andcan be attached to the first piece 38-1 at or near an outer diameterportion of the first piece 38-1. The third piece 38-3 can also have agenerally planar, disk-like shape, and can be attached to the secondpiece 38-2 at or near an outer diameter portion of the second piece38-2. In the illustrated embodiment, the first and third pieces 38-1 and38-3 are substantially axially aligned, while the second piece 38-2 isaxially offset (e.g., toward a rear side of the clutch 30). The fourthpiece 38-4 can be attached to the third piece 38-3 at or near an outerdiameter portion of the third piece 38-3, and can extend away from thethird piece 38-3 as measured in the axial direction. Accordingly, thefirst, second and third pieces 38-1 to 38-3 can all generally face therotor disk 34, while the fourth piece 38-4 can generally face away fromthe rotor disk 34. Some or all of the pieces 38-1 to 38-4 can form acorresponding portion of a wall (i.e., reservoir wall or boundary wall)of the reservoir 38. In that way, the pieces 38-1 to 38-4 of thereservoir 38 can collectively provide a volume for storing the shearfluid defined within a boundary established by the wall. The variouspieces of the reservoir 38 can be attached together in any suitablemanner, such as using welding, brazing, mechanical fasteners, swaging,pressing, threading, adhesive, or any other suitable attachment,joining, connecting or bonding method. The particular configuration ofthe reservoir 38 and associated sub-components illustrated in thefigures and described herein are merely examples, and persons ofordinary skill in the art will appreciate that further embodiments arepossible, as desired for particular applications.

FIG. 3 is a cross-sectional view of the fourth (or cap) piece 38-4,shown in isolation. As shown in the illustrated embodiment, the fourth(or cap) piece 38-4 has a first portion 38-4 a that can extend generallyaxially, a second portion 38-4 b extending generally radially from thefirst portion 38-4 a, and a ridge portion 38-4 c that is connected tothe second portion 38-4 b generally opposite the first portion 38-4 a.The ridge portion 38-4 c is generally toroidal in shape and can includea generally axially extending first part 38-4 c′, a second part 38-4 c″,and a third part 38-4 c′″. The second part 38-4 c″ can be curved, andcan join the first and third parts 39-4 c′ and 39-4 c′″ (which can belocated away from each other, spaced apart by the second part 38-4 c″).The first part 38-4 c′ can be substantially cylindrical in shape andarranged generally axially, that is, extending generally parallel to theaxis A. The third part 38-4 c′″ can be substantially frusto-conical inshape and orientated at a different angle than the first part 38-4 c′relative to the axis A. In the illustrated embodiment, the third part38-4 c′″ has a distal end angled away from the first part 38-4 c′. Thefirst part 38-4 c′ can be located at a radially outward portion of theridge 38-4 c, and the third part 38-4 c′″ can be located at a radiallyinward portion of the ridge 38-4 c. Further, the third part 38-4 c′″ canextend to an edge of the boundary wall of the reservoir 38. The ridgeportion 38-4 c provides space to accommodate protrusion of the secondend 48-2 of the flux insert 48 out of the housing 36. That is, the ridgeportion 38-4 c can wrap around the second end 48-2 of the flux insert48. In that way, the second end 48-2 of the flux insert 48 can extend atleast partially into the ridge portion 38-4 c with an axial overlap. Agroove 36-4 can be provided in the housing 36 adjacent to the second end48-2 of the flux insert 48, and the third part 38-4 c′″ can at leastpartially extend into the groove 36-4. In the illustrated embodiment,the ridge portion 38-4 c can surround and radially traverse theprotruding second end 48-2 of the flux insert 48, which can help keepshear fluid away from the flux insert 48 and help reduce a risk of fluidleakage while still being closely spaced from the base 36-1 of thehousing 36 to help maximize storage volume within the reservoir 38 andminimize a flux gap between the reservoir 38 and the flux insert 48.Furthermore, the ridge portion 38-4 c exposes a relatively large surfacearea to the flux insert 48, to help maximize flux transmission, asdescribed further below.

Turning again to FIGS. 1 and 2, the reservoir 38 as shown in theillustrated embodiment is separate from the rotor disk 34 and isindependently supported on the drive shaft 32. More specifically, thereservoir 38 can be attached to the drive shaft 32 at a different axiallocation than the rotor disk 34. A spacer 50, which can be made of anon-magnetic flux conductive material (e.g., austenitic stainlesssteel), can be positioned on the drive shaft 32 between the rotor disk34 and the reservoir 38. The valve assembly 42 can be substantiallyaxially aligned with the spacer 50 in some embodiments. Additionally, orin the alternative, another spacer 52 can be positioned between thereservoir 38 and the bearings 46 that support the housing 36. The spacer52 can also which can be made of a non-magnetic flux conductive material(e.g., austenitic stainless steel). The spacers 50 and 52 can helpprovide desired axial spacing of various components along the driveshaft 32, and can further facilitate magnetic separation or isolationbetween components on opposing sides of each spacer 50 and 52. When theclutch 30 is fully assembled, a compressive load can optionally beapplied to help hold a stack of components on the drive shaft 32, whichcan hold the spacers 50 and/or 52 in physical contact with adjacentcomponents.

Portions of the reservoir 38 can be made of steel, iron, aluminum,stainless steel or any combination of these materials, or other suitablematerials. For example, in the illustrated embodiment, the first, thirdand fourth pieces 38-1, 38-3 and 38-4 of the reservoir 38 are made of amagnetic flux conducting material (e.g., ferromagnetic materials),whereas the second piece 38-2 is made of a non-magnetic flux conductingmaterial (e.g., austenitic stainless steel, aluminum, etc.). With such aconfiguration, one or more portions of the reservoir 38 can form a partof a flux circuit for the clutch. Further, the second piece 38-2 caninterrupt magnetic flux transmission through the remainder of thereservoir 38, thereby providing magnetic separation or isolation betweenthe first piece 38-1 and both the third and fourth piece 38-3 and 38-4,and allowing different magnetic flux conductive portions of thereservoir 38 to form different portions of the overall magnetic fluxcircuit of the clutch 30. Alternatively, or in addition, one or moreadditional flux inserts and/or flux guiding pieces can be inserted intoor otherwise attached to the reservoir 38 to provide a flux path throughor around the reservoir 38. Magnetic flux transmission within the clutch30 is discussed further below.

A supply bore 54, governed by the valve assembly 42, can be provided onthe reservoir 38 to allow shear fluid to exit the reservoir 38 and passtoward the working chamber 40. In the illustrated embodiment, the supplybore 54 is located near an outer diameter of the third piece 38-3 of thereservoir 38 and faces the rotor disk 34, but could be positionedelsewhere on the reservoir 38 in alternative embodiments.

FIG. 4 is a perspective view of the rotor disk 34 and the reservoir 38shown in isolation. As shown in the illustrated embodiment, the holes(or windows) 34-5 in the rotor disk 34 have a first, radially innerportion 34-5 a that is rectangular and approximately square in shape,and a second, radially outer portion 34-5 b that is elongate in shapeand narrower (in a circumferential direction) than the first portion34-5 a. The first and second portions 34-5 a and 34-5 b can becontiguous and in fluid communication with each other, and can eachextend entirely through an axial thickness of the rotor disk 34 (i.e.,extending between opposite front and rear sides of the rotor disk 34).As shown in FIG. 4, the first portion 34-5 a can generally align oroverlap with an outer diameter portion of the reservoir 38, while thesecond portion 34-5 b can be located generally radially outward of thereservoir 38 and can extend into an outer diameter region of the rotordisk 34 where ribs extend from the rotor disk 34 and the working chamber40 (see FIG. 1) is defined. Any desired number of angularly spaced holes34-5 can be provided in the rotor disk 34. Six holes 34-5 are shown inthe illustrated embodiment, but merely by way of example and notlimitation. One or more of the holes 34-5 can be positioned atapproximately the same radial distance from the axis A as the supplybore 54, that is, the holes 34-5, or at least the first portion 34-5 a,can be located at a common radial position with the supply bore 54. Thesupply bore 54 is shown in FIG. 4 radially aligned and angularly aligned(clocked) with one of the holes 34-5 in the rotor disk 34 (e.g., alignedwith the first portion 34-5 a), such that shear fluid exiting the supplybore 54 is presented with a substantially clear, line-of-sight paththrough one of the holes 34-5, allowing the shear fluid to passsubstantially unobstructed from the supply bore 54 to an opposite(front) side of the rotor disk 34 in generally the axial direction. Inother words a center of the supply bore 54 is arranged at an angle α(measured about the axis A) relative to a center of the hole 34-5, andin the illustrated embodiment the angle a is approximately 0°. However,in further embodiments, the supply bore 54 can be positioned at a rangeof angle offsets (clocking positions) relative to the rotor disk 34 tohelp provide relatively faster or slower shear fluid flow toward andthrough the working chamber 40. The angle α can be selected to positionthe supply bore 54 at any angularly offset position between adjacentholes 34-5. For example, the angle a can be selected to have any desiredangular offset, continuously variable within a range of approximately+/−60° (clockwise or counter-clockwise). In a further preferredembodiment, the angle α can be selected within a range of approximately+/−30°, or within a range of +/−15°, or any other desired range. Morespecifically, the angle a can be selected as 60°, 30°, 15°, −60°, −30°,−15°, etc. in certain embodiments. In still further embodiments, theangle α can be selected to be +/−360°/(n·2), where n is a total numberof the holes 34-5 in the rotor disk 34 and the angle a represents theangular offset between the supply bore 54 and an adjacent one of the nholes 34-5. For illustrative purposes, a possible alternate, offsetposition of the supply bore 54′ is shown in phantom. In someembodiments, the supply bore 54 (or 54′) is offset by the angle a suchthat the supply bore 54 is angularly or circumferentially spaced fromany of the holes 34-5 in the rotor disk 34, that is, so that the bore54′ is not angularly aligned with any of the holes 34-5. Such a spaced,offset embodiment tends to slow the flow of shear fluid toward andthrough the working chamber 40 along a fluid supply path, because thereis no clear, line-of-sight path from the bore 54′ through one of theholes 34-5 in generally the axial direction. In this way, the clockingof the supply bore 54 relative to the holes 34-5 can allow foradjustment of operating characteristics of the clutch 30 in a fairlyeasy manner. For instance, clocking of the rotor disk 34 and/or thereservoir 38 can be adjusted during assembly of the clutch 30 withoutrequiring redesign of the clutch 30.

Turning again to FIG. 1, the working chamber 40 is defined between therotor disk 34 and the housing 36, and the shear fluid can be selectivelyintroduced to the working chamber 40 to selectively couple the rotordisk 34 and the housing 36 to transmit torque. The working chamber 40and the reservoir 38 can be part of a fluid circuit that includes thesupply path and a return path. As shown in the illustrated embodiment,the supply bore 54 on the reservoir 38 can be selectively covered anduncovered by the valve assembly 42 to selectively pass the shear fluidto the working chamber 40 along the supply path. Fluid in the workingchamber 40 can be returned to the reservoir 38 along the return path bypassing through a return bore 56. A pump element (not specificallyshown) can optionally be provided at or along the working chamber 40 tohelp pump the shear fluid from the working chamber 40 to the reservoir38 in a conventional manner. Generally radially extending grooves 36-5(e.g., interruptions of circumferential ribs, depressions, etc.) can beprovided in the housing 36 (or alternatively in the rotor disk 34) alongthe working chamber 40 to facilitate flow of the shear fluid.

In the illustrated embodiment, as shown in FIGS. 1 and 2, the returnbore 56 extends from the working chamber 40 through the body 36-1 of thehousing 36. The return bore 56 can pass through one of the openings 48-3in the flux insert 48, thereby facilitating a compact overall clutchdesign. An outlet 56-1 of the return bore 56 allows shear fluid to passfrom the return bore 56 to the reservoir 38. In the illustratedembodiment, the outlet 56-1 is configured as a tapered slot (e.g.,tapered in a generally radial direction with a mouth that is wider thanan interior portion) located generally radially inward from the fluxinsert 48, with the outlet 56-1 positioned adjacent to the groove 36-4in the housing 36 and the ridge 38-4 c in the reservoir 38. The taper ofthe outlet 56-1, together with the overlap of the groove 36-4 and thethird part 38-4 c′″ of the ridge 38-4 c allows the shear fluid to passrelatively smoothly and easily radially outwardly into the reservoir 38,without significant risk of obstruction or leakage (such as thatpotentially caused by the protrusion of the flux insert 48).

The valve assembly 42 in the illustrated embodiment is configured tooperate in a manner similar to that disclosed in commonly-assigned PCTPublication No. WO 2012/024497, entitled “Viscous Clutch ValveAssembly.” The valve assembly 42 can include a generally axiallypivoting armature 42-1 and a generally axially pivoting reed valve 42-2,though in alternative embodiments other types of valve assemblies can beutilized, such as those utilizing rotating valve elements, translatingvalve elements, etc. In the illustrated embodiment, the valve assembly42 is attached to the reservoir and, in the axial direction, ispositioned, at least partially, in a gap located in between thereservoir 38 and the rotor disk 34, and likewise in between the rotordisk 34 and the electromagnetic coil 44. During operation, the valveassembly 42 (including the armature 42-1 and the reed valve 42-2) ispivotable between a first, open position and a second, closed position,with the valve assembly positioned in between the rotor disk 34 and thereservoir 38 in both the first and second positions. FIGS. 1 and 2illustrate the valve assembly 42 in the first, open position. Aspreviously noted, the optional notch 34-4 in the rotor disk 34 canprovide added clearance for pivoting of the valve assembly 42, and inparticular for the armature 42-1 when the valve assembly 42 is in thefirst, open position. Although a variety of manufacturing processes canbe used, rivets or other suitable fasteners can be secured to thereservoir 38 to connect the armature 42-1 by way of an anchor spring42-3 (e.g., a leaf spring), which can provide a relatively highlyreliable steel-to-steel connection. If the armature 42-1 and the anchorspring 42-3 were attached to the rotor disk 34 as in various prior artconfigurations, an aluminum rivet-to-steel connection would typically beprovided, which would be less reliable.

As best shown in FIG. 2, the illustrated embodiment of the valveassembly 42 includes the anchor spring 42-3 attached to the third piece38-3 of the reservoir 38, and the armature 42-1 in turn attached to theanchor spring 42-3 in a pivotable configuration. The armature 42-1 canhave a generally flat or planar shape, with a ring-shaped base portion42-1 a having a central opening 42-1 a′ that surrounds the drive shaft32 as well as an extension 42-lb that radially protrudes from the baseportion 42-1 a. The base portion 42-1 a can have a sufficient radialdimension to span the second piece 38-2 of the reservoir 38, allowingthe armature 42-1 to contact both the first and third pieces 38-1 and38-3 of the reservoir 38 during certain operating conditions. Theextension 42-1 b can be located diametrically opposite the anchor spring42-3, relative to the axis A. In the illustrated embodiment, theextension 42-1 b is configured like a generally rectangular loop, withan internal opening 42-1 b′ that is contiguous with, and merges with,the central opening 42-1 a′. The openings 42-1 a′and 42-1 b′ can helpreduce weight of the valve assembly 42 and help accommodate packagingthe clutch 30 around the drive shaft 32. Furthermore, the reed valve42-2 can be separately attached to the reservoir 38 from the armature42-1. In the illustrated embodiment, the reed valve 42-2 is attached tothe first piece 38-1 of the reservoir 38. The anchor spring 42-3 canprovide a defined bending location and prescribed rotational motion ofthe valve assembly 42, and can further provide a spring bias that tendsto force the armature 42-1 and the reed valve 42-3 closed in theillustrated embodiment. Actuation of the valve assembly, as explainedfurther below, can cause the armature 42-1 to pivot and press againstthe reed valve 42-2. The reed valve 42-2 can be biased away from thesupply bore 54 by default, and force from the armature 42-1 can overcomethe default biasing of the reed valve 42-2 such that the reed valve 42-2pivots or bends to partially or completely cover the supply bore 54. Inthis way, actuation of the valve assembly 42 allows the supply bore 54to be selectively covered and uncovered to regulate flow of the shearfluid from the reservoir 38 to the working chamber 40.

The electromagnetic coil 44 can be arranged at a rear portion of theclutch 30 and rotatably supported on the drive shaft 32 by bearings 58.A tether 60 or other suitable structure can rotationally fix theelectromagnetic coil 44 relative to a mounting location of the clutch(which can be in a vehicle, etc.). The electromagnetic coil 44 can beselectively energized in order to control operation of the valveassembly 42. A coil housing can optionally be provided around at least aportion of the electromagnetic coil 44.

In order to actuate the valve assembly 42 using the electromagneticcoil, magnetic flux can be guided through portions of the clutch 30along the flux circuit (also called a flux loop or flux path). In theillustrated embodiment, magnetic flux can be transferred along the fluxcircuit from the electromagnetic coil 44 across a gap to the flux insert48 across another gap to the reservoir 38 (e.g., the fourth and thirdpieces 38-4 and 38-3) to the valve assembly (e.g., the armature 42-1 andoptionally the reed valve 42-2), and back to the reservoir 38 (e.g., thefirst piece 38-1), to the drive shaft 32 and back to the electromagneticcoil 44.

During operation, the electromagnetic coil 44 can be selectivelyenergized to move the armature 42-1, which can in turn move the reedvalve 42-2 relative to the supply bore 54. Selective control of thevalve assembly 42 to cover and uncover the supply bore 54 over time cancontrol the amount of the shear fluid that enters the working chamber40, and in turn a degree of torque transmission by the housing 36relative to the torque input to the drive shaft 32 (and the rotor disk34). In one embodiment, the reed valve 42-2 is biased to an openposition to uncover the supply bore 54 by default, and energizing theelectromagnetic coil 44 can allow the armature 42-1 and reed valve 42-2to be moved to a closed position that at least partially covers thesupply bore 54. When moved to a closed position to cover the supply bore54, a seating portion (e.g., a distal end spaced from the fulcrum orpivot point) of the reed valve 42-2 of the valve assembly 42 can restagainst the reservoir 38. Moreover, when pulled to a closed position thevalve assembly 42 of the illustrated embodiment can move the reed valve42-2 and armature 42-1 toward both the reservoir 38 and theelectromagnetic coil 44. Pulling components of the valve assembly 42toward the electromagnetic coil 44 helps improve efficiency of fluxtransmission and valve actuation, and can facilitate the use of lesspower and/or a relatively small coil 44. In certain embodiments, pulsewidth modulation (PWM) or other suitable control methodologies can beutilized to govern energization of the electromagnetic coil 44 andactuation of the valve assembly 42.

A variety of alternative embodiments of the reservoir 38 and/or fluxcircuit of the clutch 30 are possible. For instance, FIGS. 1A-1C arecross-sectional views of possible alternate embodiments of the viscousclutch 30. In the embodiment shown in FIG. 1A, a second piece 38-2′ ofthe reservoir 38 can extend to and be connected to the drive shaft 32.The first piece 38-1 therefore need not be a structural part of thereservoir 38 in the embodiment of FIG. 1A, but can be a structurallyseparate flux guiding component of the flux circuit. In the embodimentshown in FIG. 1B, the second piece 38-2′ of the reservoir 38 can extendto and be connected to the drive shaft 32. Moreover, a spacer 50′ can beintegrally and monolithically made with a pole piece (e.g., integratingthe first piece 38-1 and the spacer 50 of previously-describedembodiments). The spacer 50′ is made of magnetically flux conductivematerial in the embodiment of FIG. 1B. Additionally, in the embodimentshown in FIG. 1C, a spacer 50″ is made of a magnetically flux conductivematerial and extends into close proximity to the armature 42-1, suchthat a radial air gap is provided within the flux circuit of the clutch30. In this way, the spacer 50″ can help to enhance operation of theflux circuit by providing an additional magnetic pathway in addition tothe first piece 38-1, albeit with a radial air gap rather than an axialair gap. In still further embodiments, the spacer 50″ and the firstpiece 38-1 can be combined into a unitary and monolithic piece.

Persons of ordinary skill in the art will recognize that the embodimentsof the present invention discussed above can provide numerous advantagesand benefits. For example, mounting the valve assembly 42 to thereservoir 38 allows the clutch 30 to have two magnetically-attractivesurfaces to pull the armature 42-1 and reed valve 42-2 closed, which cancreate higher magnetic forces compared to a singlemagnetically-attractive surface. Moreover, the armature 42-1 of thevalve assembly 42 can be pulled toward the electromagnetic coil 44,which can help improve efficiency. Additionally, magnetic flux in theflux circuit can be transferred along a path that is away from thebearing 46, helping to minimize magnetic loss. The reed valve 42-2 canbe located between the rotor disk 34 and the electromagnetic coil 44,which helps reduce an overall size of the magnetic flux circuit and cancorrespondingly help reduce the size and output requirements of theelectromagnetic coil 44. These reductions, particularly with respect tothe electromagnetic coil 44, can help reduce weight of the clutch 30 andreduce the need for additional wiring (typically copper) in theelectromagnetic coil 44. Numerous other features and benefits areobtained with the present invention beyond those explicitly mentioned.

A number of further alternative embodiments are also contemplated, someof which are described below with reference to FIGS. 5-9. In general,reference characters used in FIGS. 5-9 are similar to those used withrespect to the embodiment shown in FIGS. 1-4, but with valuesincremented by one hundred in each alternative embodiment. However, itshould be noted the alternative embodiments described below are notexhaustive of possible implementations of various aspects of the presentinvention.

FIG. 5 is a cross-sectional view of another embodiment of a viscousclutch 130. The viscous clutch 130 has many similarities to the clutch30 previously described, and therefore reference characters used in FIG.5 are similar to those used with respect to the embodiment shown inFIGS. 1-4 but with values incremented by one hundred. As shown in FIG.5, the clutch 130 includes a drive shaft 132, a rotor disk 134, ahousing 136 (with a base 136-1 and a cover 136-2), a reservoir 138, aworking chamber 140, a valve assembly 142, an electromagnetic coil 144,bearings 146, a flux insert 148 (having a first end 148-1, a second end148-2, and an opening 148-3), spacers 150 and 152, a supply bore 154, areturn bore 156 with a slot-shaped outlet 156-1, and bearings 158. Theclutch 130 can function in a similar manner to that described withrespect to the clutch 30. Some notable differences in the clutch 130include a different shape of the flux insert 148 (compared to the fluxinsert 48), and a different configuration of the reservoir 138 (comparedto the reservoir 38). The reservoir 138 can include first piece 138-1,second piece 138-2, third piece 138-3 and fourth piece 138-4. The secondpiece can be made of a non-magnetic flux conducting material, while thefirst, third and fourth pieces 138-1, 138-3 and 138-4 can each be madeof magnetic flux conducting material. The second piece 138-2 can be agenerally planar disk-shaped member that radially extends between thedrive shaft 132 and the fourth piece 138-4, and can help magneticallyseparate or isolate the first piece 138-1 from the third and fourthpieces 138-3 and 138-4. The second end 148-2 of the flux insert 148 caninclude a tapered and radially outwardly extending portion, and can bearranged substantially flush with an interior wall of the base 136-1 ofthe housing 136.

FIG. 6 is a cross-sectional view of another embodiment of a viscousclutch 230. The clutch 230 is similar in many respects to theembodiments of clutches 30 and 130 described above, and thereforereference characters used in FIG. 6 are similar to those used withrespect to the embodiments shown in FIGS. 1-5 but with valuesincremented by one hundred above those in FIG. 5. As shown in FIG. 6,the clutch 230 includes a drive shaft 232, a rotor disk 134, a housing236 (with a base 236-1 and a cover 236-2), a reservoir 238 (having aridge portion 238c), a working chamber 240, a valve assembly 242 (withan armature 242-1 and a valve arm 242-2), an electromagnetic coil 244,bearings 246, a flux insert 248, a supply bore 254, and bearings 258. Itshould be noted that a return bore in the housing 236 is not shown inFIG. 6 for simplicity, but can be provided in a manner similar to thatshow and described with respect to the preceding embodiments. The clutch230 can function in a similar manner to that described with respect tothe embodiments of clutches 30 and 130.

FIG. 7 is a partial cross-sectional view of another embodiment of aviscous clutch 330. The clutch 330 is similar in many respects to theembodiments of clutches 30, 130 and 230 described above, and thereforereference characters used in FIG. 7 are similar to those used withrespect to the embodiments shown in FIGS. 1-6 but with valuesincremented by one hundred above those in FIG. 6. As shown in FIG. 7,the clutch 330 includes a drive shaft 332, a rotor disk 334, a housing336 (with a base 336-1 and a cover 336-2), a reservoir 338, a workingchamber 340, a valve assembly 342 (with an armature 342-1 and a valvearm 342-2), an electromagnetic coil 344, bearings 346, a flux insert348, a spacer 252, a supply bore 354, bearings 358 and a mounting plate370. It should be noted that a return bore in the housing 336 is notshown in FIG. 7 for simplicity, but can be provided in a manner similarto that show and described with respect to the preceding embodiments.The clutch 330 can function in a similar manner to that described withrespect to the embodiments of clutches 30, 130 and 230. However, in theembodiment of FIG. 7, the reservoir 338 is attached to a front side ofthe rotor disk 334, opposite the electromagnetic coil 344. The valveassembly 342 can be attached to the mounting plate 370 that in turn ismounted to the shaft 332 separate from the rotor disk 334. In that waythe valve assembly 342 is located at a rear side of the rotor disk 334.The non-magnetic bearing spacer 352 can be provided between the mountingplate 370 and the bearing 346 that supports the housing 336. Themounting plate 370 can be made of magnetic flux conductive material. Aflux path of the clutch 330 can be provided as follows: from theelectromagnetic coil 344 to the flux insert 348 to the armature 342-1(and optionally the valve arm 342-2) to the mounting plate 370 to thedrive shaft 332 and back to the electromagnetic coil 344.

FIG. 8 is a partial cross-sectional view of another embodiment of aviscous clutch 430. The clutch 430 is similar in many respects to theembodiments of clutches 30, 130, 230 and 330 described above, andtherefore reference characters used in FIG. 8 are similar to those usedwith respect to the embodiments shown in FIGS. 1-7 but with valuesincremented by one hundred above those in FIG. 7. As shown in FIG. 8,the clutch 430 includes a drive shaft 432, a rotor disk 434, a housing436 (with a base 436-1 and a cover 436-2), a reservoir 438, a workingchamber 440, a valve assembly 442 (with an armature 442-1 and a valvearm 442-2), an electromagnetic coil 444, bearings 446, a flux insert448, a spacer 452, a supply bore 454, bearings 458 and a mounting plate470. It should be noted that a return bore in the housing 436 is notshown in FIG. 8 for simplicity, but can be provided in a manner similarto that show and described with respect to the preceding embodiments.The clutch 430 can function in a similar manner to that described withrespect to the embodiments of clutches 30, 130, 230 and 330. However,the clutch 430 has a different configuration of the mounting plate 470that spaces the valve arm 442-2 further from the rotor disk 434, and thereservoir 438 is attached to a front side of the rotor disk 434,opposite the electromagnetic coil 444. An integrated spacer portion470-1 is provided with the mounting plate 470 as shown in FIG. 8. Inalternative embodiments, a separate piece (not shown) can be providedbetween the mounting plate 470 and the rotor disk 434, such as a spacer(e.g., similar to spacer 50 described above with respect to anotherembodiment) that can magnetically isolate the mounting plate 470 fromthe rotor disk 434.

FIG. 9 is a partial cross-sectional view of yet another embodiment of aviscous clutch 530. The clutch 530 is similar in many respects to theembodiments of clutches 30, 130, 230, 330 and 430 described above, andtherefore reference characters used in FIG. 9 are similar to those usedwith respect to the embodiments shown in FIGS. 1-8 but with valuesincremented by one hundred above those in FIG. 8. As shown in FIG. 9,the clutch 530 includes a drive shaft 532, a rotor disk 534, a housing536 (with a base 536-1 and a cover 536-2), a reservoir 538, a workingchamber 540, a valve assembly 542 (with a control pin 542-0, an armature542-1 and a valve arm 542-2), an electromagnetic coil 544, bearings 546,a flux insert 548, a spacer 552, a supply bore 554, a return bore 556and bearings 558. The clutch 530 can function in a similar manner tothat described with respect to the embodiments of clutches 30, 130, 230,330 and 430. However, in the embodiment of the clutch 530 shown in FIG.9, the reservoir 538 is attached to a rear side of the rotor disk 534.Furthermore, the valve assembly 542 can have a difference configuration,similar in some respects to the valve configuration disclosed incommonly-assigned PCT Application No. PCT/US13/60889. The armature 542-1can be located at a rear side of the rotor disk 534 and the valve arm542-2 can be located at a front side of the rotor disk 534, with one ormore control pins 542-0 extending through rotor disk 534 to connect thearmature 542-1 and the valve arm 542-2. The valve arm 542-2 can beaffixed to the rotor disk 534 and the control pin 542-0 engaged with thevalve arm 542-2 at a location spaced from a fulcrum or pivot point ofthe valve arm 542-2. In further embodiments, an additional spacer (notshown) can be provided between the spacer 552 and the bearing 546 thatsupports the housing 536, such as an additional spacer (e.g., similar tospacer 50 described above with respect to another embodiment) that canmagnetically isolate the spacer 552 from the bearing 546. A flux path ofthe clutch 530 can be provided as follows: from the electromagnetic coil544 to the flux insert 548 to the armature 542-1 (and optionally thecontrol pin 542-0 and/or the valve arm 542-2) to the spacer 552 to thedrive shaft 532 and back to the electromagnetic coil 544.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A viscous clutch comprising: a shaft; a rotor attached to the shaft; ahousing located adjacent to the rotor; a working chamber defined betweenthe rotor and the housing; and a reservoir used to store a shear fluid,wherein selective introduction of the shear fluid to the working chamberfacilitates selective torque transmission between the rotor and thehousing, and wherein the reservoir is attached to the shaft separatelyfrom the rotor.

The viscous clutch of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

the reservoir can be attached to the shaft at a location axially spacedfrom a location at which the rotor is attached to the shaft;

a spacer positioned in between the reservoir and the rotor on the shaft;

a valve assembly configured to control flow of the shear fluid to theworking chamber, wherein the valve assembly is positioned in between thereservoir and the rotor; and an electromagnetic coil, wherein selectiveenergization of the electromagnetic coil governs actuation of the valveassembly;

a notch in the rotor configured to create a space to accommodate atleast a portion of the valve assembly;

a flux insert positioned adjacent to the electromagnetic coil to passmagnetic flux along a portion of a flux circuit that connects theelectromagnetic coil and the valve assembly, wherein the flux insert hasan opening; and a return bore extending from the working chamber to thereservoir to provide at least a portion of a return path to return theshear fluid from the working chamber to the reservoir, the return borepassing through the opening in the flux insert;

a ridge in a reservoir wall of the reservoir; and a flux insertpositioned adjacent to the electromagnetic coil to pass magnetic fluxalong a portion of a flux circuit that connects the electromagnetic coiland the valve assembly, wherein the ridge of the reservoir wall at leastpartially wraps around an end of the flux insert;

a groove defined in the housing adjacent to the flux insert, wherein theridge of the reservoir wall extends at least partially into the groove;

the ridge of the reservoir wall can include a first part, a second partconnected to the first part, and a third part connected to the secondpart away from the first part, wherein the third part is substantiallyfrusto-conical in shape;

the third part can be located at a radially inward edge of the ridge ofthe reservoir wall;

the reservoir can have a multi-piece construction, wherein at least twopieces of the reservoir are made of a magnetic flux conducting material,and wherein at least one piece of the reservoir is made of anon-magnetic flux conducting material such that the at least one piecemade of the non-magnetic flux conducting material isolates differentmagnetic flux conductive portions of the reservoir;

the reservoir can include a first magnetic flux conducting portionlocated radially outward of the shaft and a second magnetic fluxconducting portion located radially outward of the shaft, wherein thefirst and second magnetic flux conducting portions are magneticallyseparated from one another;

a substantially disk-shaped inner piece; a substantially disk-shapedintermediate piece attached to the inner piece; a substantiallydisk-shaped outer piece attached to the intermediate piece; and a cappiece attached to the outer piece, wherein the cap piece extends awayfrom the outer piece in the axial direction;

the inner piece, the outer piece and the cap piece can each be made of amagnetic flux conducting material, and the intermediate piece can bemade of a non-magnetic flux conducting material;

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the rotor, wherein the hole and the supplybore are located at a common radial position, and wherein an angle abetween the hole and the supply bore relative to an axis of the viscousclutch is within a range of approximately −60°≦α≦60°, or alternativelyapproximately −30°≦α≦30°, or alternatively approximately −15°≦α≦15°;

wherein a total of n holes are providing in the rotor, and wherein theangle α between the hole and the supply bore relative to the axis of theviscous clutch is +/−360°/(n·2);

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the rotor, wherein the hole and the supplybore are aligned in a line-of-sight relationship;

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the rotor, wherein the hole and the supplybore are angularly offset from each other, such that supply bore isangularly spaced from the hole;

a return bore extending from the working chamber to the reservoir toprovide at least a portion of a return path to return the shear fluidfrom the working chamber to the reservoir, wherein the return bore has aslot-shaped outlet; and/or

the slot-shaped outlet can be tapered.

A method for use with a viscous clutch, the method comprising: rotatinga rotor disk; rotating a reservoir with the rotor disk; and pivoting avalve assembly between a first position and a second position, whereinthe valve assembly is positioned in between the rotor disk and thereservoir in both the first and second positions.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingsteps, features, and/or configurations:

energizing an electromagnetic coil to generate magnetic flux; andtransmitting the magnetic flux from the electromagnetic coil along aflux circuit to actuate the valve assembly, the step comprising:transmitting magnetic flux along the flux circuit from theelectromagnetic coil toward the valve assembly through a first portionof the reservoir; and transmitting magnetic flux along the flux circuitfrom the valve assembly toward the electromagnetic coil through a secondportion of the reservoir.

A method for use with a viscous clutch, the method comprising:energizing an electromagnetic coil to generate magnetic flux; andtransmitting the magnetic flux from the electromagnetic coil along aflux circuit to actuate a valve assembly, the step comprising:transmitting magnetic flux along the flux circuit from theelectromagnetic coil toward the valve assembly through a first portionof a reservoir; and transmitting magnetic flux along the flux circuitfrom the valve assembly toward the electromagnetic coil through a secondportion of the reservoir.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingsteps, features, and/or configurations:

pivoting a valve assembly between a first position and a secondposition, wherein the valve assembly is positioned in between a rotordisk and the reservoir in both the first and second positions.

A viscous clutch comprising: a shaft capable of rotation with a torqueinput; an input member fixedly attached to the shaft to rotatetherewith; an output member located adjacent to the input member; aworking chamber defined between the input member and the output member,wherein selective introduction of a shear fluid to the working chamberfacilitates selective torque transmission between the input member andthe output member; and a reservoir fixedly attached to the shaft at alocation axially spaced from the input member, and configured to rotatetherewith, the reservoir being capable of storing a supply of the shearfluid.

A viscous clutch comprising: a rotatable input member; a rotatableoutput member located adjacent to the input member; a working chamberdefined between the input member and the output member, whereinselective introduction of a shear fluid to the working chamberfacilitates selective torque transmission between the input member andthe output member; a rotatable reservoir having a wall facing the inputmember and axially spaced from the input member, the reservoirconfigured to rotate with the input member and to store a supply of theshear fluid; a supply bore in the reservoir to allow the shear fluid toexit the reservoir; and a total of n holes in the input member, whereinthe supply bore and an adjacent one of the n holes are located at acommon radial position, and wherein an angle a between the adjacent holeand the supply bore relative to the axis of the viscous clutch is+/−360°/(n·2).

The viscous clutch of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

the angle α between the adjacent hole and the supply bore relative tothe axis of the viscous clutch can be within a range of approximately−60°≦α≦60°, or alternatively approximately −30°≦α≦30°, or alternativelyapproximately −15°≦α≦15°;

the hole and the supply bore can be aligned in a line-of-sightrelationship; and/or

the hole and the supply bore can be angularly offset from each other,such that supply bore is angularly spaced from the hole.

A viscous clutch comprising: an input member; an output member locatedadjacent to the input member; a working chamber defined between theinput member and the output member; a reservoir for storing a supply ofa shear fluid capable of creating a viscous torque coupling between theinput member and the output member when the shear fluid is introducedinto the working chamber, wherein the reservoir includes a reservoirwall having a ridge; a valve assembly configured to control flow of theshear fluid to the working chamber; an electromagnetic coil capable ofbeing energized to selectively actuate the valve assembly; and a fluxinsert positioned adjacent to the electromagnetic coil to pass magneticflux along a portion of a flux circuit that connects the electromagneticcoil and the valve assembly, wherein the ridge of the reservoir wall atleast partially wraps around an end of the flux insert.

The viscous clutch of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

the flux insert can extend through the output member and protrudes fromthe output member;

a groove defined in the output member adjacent to the flux insert,wherein the ridge of the reservoir wall extends at least partially intothe groove;

the ridge of the reservoir wall can include a first part, a second partconnected to the first part, and a third part connected to the secondpart away from the first part, and the third part can be substantiallyfrusto-conical in shape;

the third part can be located at a radially inward edge of the ridge ofthe reservoir wall;

a groove defined in the output member adjacent to the flux insert,wherein the third part of the ridge of the reservoir wall extends atleast partially into the groove;

a shaft, wherein the input member is a rotor disk attached to the shaft,and wherein the output member is a housing rotatably supported on theshaft;

the reservoir can include a first magnetic flux conducting portionlocated radially outward of the shaft and a second magnetic fluxconducting portion located radially outward of the shaft, wherein thefirst and second magnetic flux conducting portions are magneticallyseparated from one another;

the reservoir can have a multi-piece construction, wherein at least twopieces of the reservoir are made of a magnetic flux conducting material,and wherein at least one piece of the reservoir is made of anon-magnetic flux conducting material such that the at least one piecemade of the non-magnetic flux conducting material isolates differentmagnetic flux conductive portions of the reservoir;

the reservoir can further comprise: a substantially disk-shaped innerpiece; a substantially disk-shaped intermediate piece attached to theinner piece; a substantially disk-shaped outer piece attached to theintermediate piece; and a cap piece attached to the outer piece, whereinthe cap piece extends away from the outer piece in the axial direction;

the inner piece, the outer piece and the cap piece can each be made of amagnetic flux conducting material, and the intermediate piece can bemade of a non-magnetic flux conducting material;

a return bore extending from the working chamber to the reservoir toprovide at least a portion of a return path to return the shear fluidfrom the working chamber to the reservoir, wherein the flux insert hasan opening, and wherein the return bore passes through the opening inthe flux insert;

a return bore extending from the working chamber to the reservoir toprovide at least a portion of a return path to return the shear fluidfrom the working chamber to the reservoir, wherein the return bore has aslot-shaped outlet;

the slot-shaped outlet can be tapered, such as by being radiallytapered;

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the input member, wherein the hole and thesupply bore are located at a common radial position, and wherein anangle a between the hole and the supply bore relative to an axis of theviscous clutch is within a range of approximately −60°≦α≦60°, oralternatively approximately −30°≦α≦30°, or alternatively approximately−15°≦α≦15°;

wherein a total of n holes are providing in the rotor, and wherein theangle α between the hole and the supply bore relative to the axis of theviscous clutch is +/−360°/(n·2);

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the input member, wherein the hole and thesupply bore are aligned in a line-of-sight relationship; and/or

a supply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the input member, wherein the hole and thesupply bore are angularly offset from each other, such that supply boreis angularly spaced from the hole.

A viscous clutch comprising: an input member; an output member locatedadjacent to the input member; a working chamber defined between theinput member and the output member; a reservoir for storing a supply ofa shear fluid capable of creating a viscous torque coupling between theinput member and the output member when introduced into the workingchamber; a valve assembly configured to control flow of the shear fluidthrough the working chamber; an electromagnetic coil energizeable toselectively actuate the valve assembly; a flux insert positionedadjacent to (but not necessarily directly adjoining) the electromagneticcoil to pass magnetic flux along a portion of a flux circuit thatconnects the electromagnetic coil and the valve assembly, wherein theflux insert has an opening; and a return bore extending from the workingchamber to the reservoir to provide at least a portion of a return pathto return the shear fluid from the working chamber to the reservoir, thereturn bore passing through the opening in the flux insert.

The viscous clutch of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

the return bore can have a slot-shaped outlet;

the slot-shaped outlet can be tapered;

the slot-shaped outlet can be radially tapered;

the output member can comprise a housing, and the return bore can extendthrough the housing;

a supply bore through the reservoir to allow the shear fluid to exit thereservoir; and a hole in the input member, wherein the hole and thesupply bore are located at a common radial position, and wherein anangle a between the hole and the supply bore relative to an axis of theviscous clutch is within a range of approximately −60°≦α≦60°, oralternatively approximately −30°≦α≦30°, or alternatively approximately−15°≦α≦15°;

wherein a total of n holes are providing in the rotor, and wherein theangle α between the hole and the supply bore relative to the axis of theviscous clutch is +/−360°/(n·2);

a supply bore through the reservoir to allow the shear fluid to exit thereservoir; and a hole in the input member, wherein the hole and thesupply bore are aligned in a line-of-sight relationship; and/or

a supply bore through the reservoir to allow the shear fluid to exit thereservoir; and a hole in the input member, wherein the hole and thesupply bore are angularly offset from each other, such that supply boreis angularly spaced from the hole.

Summation

Any relative terms or terms of degree used herein, such as“substantially”, “essentially”, “generally”, “approximately” and thelike, should be interpreted in accordance with and subject to anyapplicable definitions or limits expressly stated herein. In allinstances, any relative terms or terms of degree used herein should beinterpreted to broadly encompass any relevant disclosed embodiments aswell as such ranges or variations as would be understood by a person ofordinary skill in the art in view of the entirety of the presentdisclosure, such as to encompass ordinary manufacturing tolerancevariations, incidental alignment variations, alignment or shapevariations induced by thermal, rotational or vibrational operationalconditions, and the like.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. For example, the disclosed clutchembodiments could be operated with torque inputs and outputs reversed.Moreover, spacers used within embodiments of the clutch can be eithermagnetically flux conductive or non-magnetically flux conductive, asdesired for particular applications. Additionally, features described orshown with respect to one embodiment can be incorporated into nearly anyother embodiment as desired.

The invention claimed is:
 1. A viscous clutch comprising: a shaft; arotor attached to the shaft in a rotationally fixed relationship; ahousing located adjacent to the rotor; a working chamber defined betweenthe rotor and the housing; and a reservoir defining a volume used tostore a shear fluid, wherein selective introduction of the shear fluidto the working chamber facilitates selective torque transmission betweenthe rotor and the housing, wherein the reservoir is rotationally fixedto the shaft, and wherein the reservoir is attached to the shaftseparately from the rotor.
 2. The viscous clutch of claim 1, wherein thereservoir is attached to the shaft at a location axially spaced from alocation at which the rotor is attached to the shaft.
 3. The viscousclutch of claim 2 and further comprising: a spacer positioned in betweenthe reservoir and the rotor on the shaft.
 4. The viscous clutch of claim1 and further comprising: a valve assembly configured to control flow ofthe shear fluid to the working chamber, wherein the valve assembly ispositioned in between the reservoir and the rotor; and anelectromagnetic coil, wherein selective energization of theelectromagnetic coil governs actuation of the valve assembly.
 5. Theviscous clutch of claim 4 and further comprising: a notch in the rotorconfigured to create a space to accommodate at least a portion of thevalve assembly.
 6. The viscous clutch of claim 4 and further comprising:a flux insert positioned adjacent to the electromagnetic coil to passmagnetic flux along a portion of a flux circuit that connects theelectromagnetic coil and the valve assembly, wherein the flux insert hasan opening; and a return bore extending from the working chamber to thereservoir to provide at least a portion of a return path to return theshear fluid from the working chamber to the reservoir, the return borepassing through the opening in the flux insert.
 7. The viscous clutch ofclaim 4 and further comprising: a ridge in a reservoir wall of thereservoir; and a flux insert positioned adjacent to the electromagneticcoil to pass magnetic flux along a portion of a flux circuit thatconnects the electromagnetic coil and the valve assembly, wherein theridge of the reservoir wall at least partially wraps around an end ofthe flux insert.
 8. The viscous clutch of claim 7 and furthercomprising: a groove defined in the housing adjacent to the flux insert,wherein the ridge of the reservoir wall extends at least partially intothe groove.
 9. The viscous clutch of claim 7, wherein the ridge of thereservoir wall includes a first part, a second part connected to thefirst part, and a third part connected to the second part away from thefirst part, and wherein the third part is substantially frusto-conicalin shape.
 10. The viscous clutch of claim 9, wherein the third part islocated at a radially inward edge of the ridge of the reservoir wall.11. The viscous clutch of claim 1, wherein the reservoir has amulti-piece construction, wherein at least two pieces of the reservoirare made of a magnetic flux conducting material, and wherein at leastone piece of the reservoir is made of a non-magnetic flux conductingmaterial such that the at least one piece made of the non-magnetic fluxconducting material isolates different magnetic flux conductive portionsof the reservoir.
 12. The viscous clutch of claim 1, wherein thereservoir includes a first magnetic flux conducting portion locatedradially outward of the shaft and a second magnetic flux conductingportion located radially outward of the shaft, wherein the first andsecond magnetic flux conducting portions are magnetically separated fromone another.
 13. The viscous clutch of claim 1, the reservoir furthercomprising: a substantially disk-shaped inner piece; a substantiallydisk-shaped intermediate piece attached to the inner piece; asubstantially disk-shaped outer piece attached to the intermediatepiece; and a cap piece attached to the outer piece, wherein the cappiece extends away from the outer piece in the axial direction.
 14. Theviscous clutch of claim 13, wherein the inner piece, the outer piece andthe cap piece are each made of a magnetic flux conducting material, andwherein the intermediate piece is made of a non-magnetic flux conductingmaterial.
 15. The viscous clutch of claim 1 and further comprising: asupply bore located on the reservoir to allow the shear fluid to exitthe reservoir; and a hole in the rotor, wherein the hole and the supplybore are located at a common radial position, and wherein an angle αbetween the hole and the supply bore relative to an axis of the viscousclutch is within a range of approximately −60°≦α≦α°.
 16. The viscousclutch of claim 15, wherein the angle α between the hole and the supplybore relative to the axis of the viscous clutch is within a range ofapproximately −30°≦α≦30°.
 17. The viscous clutch of claim 15, wherein atotal of n holes are providing in the rotor, and wherein the angle αbetween the hole and the supply bore relative to the axis of the viscousclutch is +/−360°/(n·2).
 18. The viscous clutch of claim 1 and furthercomprising: a supply bore located on the reservoir to allow the shearfluid to exit the reservoir; and a hole in the rotor, wherein the holeand the supply bore are aligned along an axial line.
 19. The viscousclutch of claim 1 and further comprising: a supply bore located on thereservoir to allow the shear fluid to exit the reservoir; and a hole inthe rotor, wherein the hole and the supply bore are angularly offsetfrom each other, such that supply bore is angularly spaced from thehole.
 20. The viscous clutch of claim 1 and further comprising: a returnbore extending from the working chamber to the reservoir to provide atleast a portion of a return path to return the shear fluid from theworking chamber to the reservoir, wherein the return bore has aslot-shaped outlet.
 21. The viscous clutch of claim 20, wherein theslot-shaped outlet is tapered.
 22. A viscous clutch comprising: a shaftcapable of rotation with a torque input; an input member fixedlyattached to the shaft to rotate therewith in a rotationally fixedrelationship; an output member located adjacent to the input member; aworking chamber defined between the input member and the output member,wherein selective introduction of a shear fluid to the working chamberfacilitates selective torque transmission between the input member andthe output member; and a reservoir fixedly attached to the shaft at alocation axially spaced from the input member, and configured to rotatetherewith in a rotationally fixed relationship, the reservoir defining avolume capable of storing a supply of the shear fluid.